In a switching power supply, in order to reduce the burden on power components, increase the power density, reduce the output voltage ripple, and improve the quality of the output voltage, a multi-channel power stage circuit may be adopted to convert an input voltage to an output voltage in an interleaved manner, where each of the power stage circuits is operated in order. Currently, a control signal of a multi-channel power stage circuit in an interleaved switching power supply may be generated by comparing a ramp signal that is generated based on an inductor current sampling signal and an output error compensation signal against a fixed threshold value. In such a control scheme, a peak value and a valley value of the ramp signal are both fixed values, so the control signal may be unable to respond quickly when the output voltage drops or rises. Thus, the output voltage of the switching power supply may not quickly recover to a desired value.